Answered: Validate that the following code, which…

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Question

Validate that the following code, which adds the
methods var() and stddev() to Accumulator, computes both the mean and variance
of the numbers presented as arguments to addDataValue():
public class Accumulator
{
private double m;
private double s;
private int N;
public void addDataValue(double x)
{
N++;
s = s + 1.0 * (N-1) / N * (x - m) * (x - m);
m = m + (x - m) / N;
}
public double mean()
{ return m; }
public double var()
{ return s/(N - 1); }
public double stddev()
{ return Math.sqrt(this.var()); }
}
This implementation is less susceptible to roundoff error than the straightforward implementation based on saving the sum of the squares of the number

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